For decades, experts have argued over when to clamp and cut a newborn's umbilical cord after birth.

Now, more health organizations are beginning to recommend delayed cord clamping. The American Congress of Obstetricians and Gynecologists has become one of the latest to advise medical professionals to wait at least 30 to 60 seconds before clamping and cutting.

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Throughout a pregnancy, the umbilical cord carries important nutrients and blood from the mother to the baby. After birth, a clamp is put on the cord, and it is cut so that the baby is no longer attached to the placenta. This procedure is one of the oldest involved in birth.

In most Western countries, including the United States, the cord is clamped immediately after birth: usually between 10 to 15 seconds after.

In the first few minutes after birth, blood is still circulating from the placenta to the infant. When clamping is put off for two or three minutes, it allows a physiological transfer of oxygen-rich blood to flow into the infant -- a process called placental transfusion.

A growing body of research shows that both full-term and preterm infants may benefit from this additional blood volume. Experts say this can affect development, especially for babies born early.

"We have known for several years that among preterm infants, delayed cord clamping reduces the risk of several serious complications of prematurity, such as anemia," Dr. Maria A. Mascola, lead author of the recommendation, wrote in an e-mail.

"In recent years, more information has accumulated that showed that even among full-term infants, delaying clamping of the baby's umbilical cord can be helpful also," she added.

Doctors traditionally cut the cord so quickly because of long-held beliefs that placental blood flow could increase birth complications such as neonatal respiratory distress, a type of blood cancer called polycythemia and jaundice from rapid transfusion of a large volume of blood.

However, recent research has shown that delayed clamping does not cause complications in either the mother or the child.

"There has also been concern about whether delayed cord clamping would pose more risk to the mother, specifically, would it lead to more risk of excessive blood loss at the time of delivery," Mascola wrote in the e-mail.

"We now have good evidence that delayed cord clamping does not add to that risk. Womens' postpartum blood counts are similar, whether they have undergone delayed cord clamping or not."

Placental transfusion in full-term infants -- babies born between 37 and 42 weeks of gestation -- has been shown to increase hemoglobin levels and provide sufficient iron reserves in the first 6 to 8 months of life, preventing or delaying an iron deficiency, according to the recommendation.

In preterm infants -- those born before 37 weeks -- delayed clamping has been associated with improved circulation in the infant's heart, better red blood cell volume and decreased need for blood transfusion. It has also been shown to lower the occurrence of brain hemorrhage and an intestinal disease called necrotizing enterocolitis.

The benefits of delayed clamping in preterm infants are clear, but in full-term infants, more research is needed, according to Dr. Colleen Denny, an OB/GYN and assistant clinical professor at the New York University School of Medicine who was not involved in the recommendation.

"Preterm infants definitely do better with delayed cord clamping," Denny said, noting that they have fewer serious problems such as brain bleeds and intestinal issues. "For term infants, we don't really have that data yet."

Other organizations have also made similar recommendations.

The World Health Organization recommends that the umbilical cord should be clamped after the first minute. However, in some babies who can't breathe on their own, the cord should be cut immediately to allow effective ventilation to be performed, it says.

The American College of Nurse-Midwives recommends delaying the clamping of the cord in full-term infants for five minutes if the newborn is placed skin-to-skin with the mother or two minutes if the newborn is at or below the height of the vaginal canal.

The American Academy of Pediatrics also recommends waiting at least 30 to 60 seconds for most newborns.

Expectant parents interested in delayed clamping should speak with their physician to ensure that both the mom and baby are in a stable condition to do so, according to Denny.

She explains to her patients that, if there is any kind of emergency with the mom or baby, they should not wait to clamp the cord.

"Even though there are benefits, the bigger benefit is getting patients the care they need right away," she said.